Default Value

Paimon allows specifying default values for columns. When users write to these tables without explicitly providing values for certain columns, Paimon automatically generates default values for these columns.

Create Table

Flink SQL does not have native support for default values, so we can only create a table without default values:

CREATE TABLE my_table (
    a BIGINT,
    b STRING,
    c INT,
    tags ARRAY<STRING>,
    properties MAP<STRING, STRING>,
    nested ROW<x INT, y STRING>
);

We support the procedure of modifying column default values in Flink. You can add default value definitions after creating the table:

-- Set simple type default values
CALL sys.alter_column_default_value('default.my_table', 'b', 'my_value');
CALL sys.alter_column_default_value('default.my_table', 'c', '5');

-- Set complex type default values
CALL sys.alter_column_default_value('default.my_table', 'tags', '[tag1, tag2, tag3]');
CALL sys.alter_column_default_value('default.my_table', 'properties', '{key1 -> value1, key2 -> value2}');
CALL sys.alter_column_default_value('default.my_table', 'nested', '{42, default_value}');

Insert Table

For SQL commands that execute table writes, such as the INSERT, UPDATE, and MERGE commands, NULL value is parsed into the default value specified for the corresponding column.

For example:

INSERT INTO my_table (a) VALUES (1), (2);

SELECT * FROM my_table;
-- result: [[1, my_value, 5, [tag1, tag2, tag3], {key1=value1, key2=value2}, +I[42, default_value]],
--          [2, my_value, 5, [tag1, tag2, tag3], {key1=value1, key2=value2}, +I[42, default_value]]]